Channeled heat dissipation device and a method of fabrication

ABSTRACT

Numerous embodiments of a channeled heat dissipation device and a method of fabrication are disclosed. In one embodiment, a channeled heat dissipation device comprises a base portion having a dissipation surface and a substantially opposed mounting surface, and at least one channel defined in the base portion, wherein said at least one channel extends from said dissipation surface to said mounting surface.

This application is a continuation application of application Ser. No.10/387,654, entitled “A Channeled Heat Dissipation Device and a Methodof Fabrication”, filed Mar. 12, 2003 now U.S. Pat. No. 6,747,873.

BACKGROUND

Higher performance, lower cost, increased miniaturization of integratedcircuit components, and greater packaging density of integrated circuitsare ongoing goals of the computer industry. As these goals are achieved,microelectronic dice become smaller. Accordingly, the density of powerconsumption of the integrated circuit components in the microelectronicdie has increased, which, in turn, increases the power requirements ofother board level components that may be associated with themicroelectronic die, such as voltage regulators, which may perform powerdelivery, for example. If the temperature of these associated componentsbecomes too high, the components may be damaged or destroyed.

Various apparatus and techniques have been used and are presently beingused for removing heat from microelectronic dice. One such heatdissipation technique involves the attachment of a high surface areaheat sink to a microelectronic die. FIG. 6 illustrates an assembly 200comprising a microelectronic die 202 (illustrated as a flip chip)physically and electrically attached to a substrate carrier 204 by aplurality of solder balls 206. A heat sink 208 is attached to a backsurface 212 of the microelectronic die 202 by a thermally conductiveadhesive 214. The heat sink 208 is usually constructed from a thermallyconductive material, such as copper, copper alloys, aluminum, aluminumalloys, or any suitable combination thereof. The heat generated by themicroelectronic die 202 is drawn into the heat sink 208 (following thepath of least thermal resistance) by conductive heat transfer.

High surface area heat sinks 208 are generally used because the rate atwhich heat is dissipated from a heat sink is substantially proportionalto the surface area of the heat sink. The high surface area heat sink208 usually includes a plurality of projections 216 extendingsubstantially perpendicularly from the microelectronic die 202. It is,of course, understood that the projections 216 may include, but are notlimited to, elongate planar fin-like structures and columnar/pillarstructures. The high surface area of the projections 216 allows heat tobe convectively dissipated from the projections 216 into the airsurrounding the high surface area heat sink 208. A fan 218 may beincorporated into the assembly 200 to enhance the convective heatdissipation. However, although high surface area heat sinks are utilizedin a variety of microelectronic applications, they may not provide heatdissipation for associated components that may be attached to thesubstrate carrier 204 (not shown). Additionally, heat sinks such as thismay reduce or block airflow to components on a substrate, therebycausing areas of air stagnation, which may result in inadequate heatdissipation for one or more of these components.

Therefore, it would be advantageous to develop apparatus and techniquesto effectively remove heat from a microelectronic die while providingsome capability for heat dissipation for other components associatedwith the die.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter regarded as embodiments of the claimed subject matteris particularly pointed out and distinctly claimed in the concludingportion of the specification. Embodiments of the claimed subject matter,however, both as to organization and method of operation, together withobjects, features, and advantages thereof, may best be understood byreference to the following detailed description when read with theaccompanying drawings in which:

FIG. 1 is a side cross-sectional view of a first embodiment of a heatdissipation device attached to a microelectronic die, according to thepresent invention;

FIG. 2 is an oblique view of the cross-sectional view of the heatdissipation device, according to the present invention;

FIG. 3 is an alternate side cross-sectional view of a second embodimentof a heat dissipation device attached to a microelectronic die,according to the present invention;

FIG. 4 is a side cross-sectional view of a third embodiment of a heatdissipation device attached to a microelectronic die, according to thepresent invention;

FIG. 5 is a bottom plan view of various components of a substrate thatmay be incorporated as part of the present invention; and

FIG. 6 is a side cross-sectional view of a heat dissipation deviceattached to a microelectronic die, as known in the art.

DETAILED DESCRIPTION

Embodiments of the claimed subject matter may comprise a channeled heatdissipation device and a method of fabrication. One particularembodiment of the claimed subject matter may comprise a heat dissipationdevice having a base portion, wherein the base portion has a dissipationsurface and a substantially opposed mounting surface, and at least onechannel formed in the base portion thereof. In this embodiment, the atleast one channel may allow air from a fan to flow through the baseportion to the substrate carrier, providing airflow to one or morecomponents formed thereon.

It is worthy to note that any reference in the specification to “oneembodiment” or “an embodiment” means that a particular feature,structure, or characteristic described in connection with the embodimentis included in at least one embodiment of the claimed subject matter.The appearances of the phrase “in one embodiment” in various places inthe specification are not necessarily all referring to the sameembodiment.

Numerous specific details may be set forth herein to provide a thoroughunderstanding of the embodiments of the claimed subject matter. It willbe understood by those skilled in the art, however, that the embodimentsof the claimed subject matter may be practiced without these specificdetails. In other instances, well-known methods, procedures andcomponents have not been described in detail so as not to obscure theembodiments of the claimed subject matter. It can be appreciated thatthe specific structural and functional details disclosed herein may berepresentative and do not necessarily limit the scope of the claimedsubject matter.

Referring now in detail to the drawings wherein like parts aredesignated by like reference numerals throughout, there is illustratedin FIG. 1 a microelectronic assembly 100 of the claimed subject mattercomprising a heat dissipation device 102 attached to a microelectronicdie 104 (illustrated as a flip chip). The microelectronic die has anactive surface physically and electrically attached to the primary side109 of a substrate carrier 108 by a plurality of solder balls 106,although, in alternative embodiments, the microelectronic die may beelectrically attached by use of a socket (not shown). The base portion118 of the heat dissipation device has a mounting surface 114, and aheat dissipation surface 116. The mounting surface 114 of the baseportion 118 of the heat dissipation device 102 is attached to the backsurface of the microelectronic die 104, preferably by a thermallyconductive adhesive (not shown), as known in the art. Although the heatdissipation device is illustrated as being attached to a microelectronicdie 104, the claimed subject matter is not so limited. The heatdissipation device 102 may be attached to any surface from which removalof heat is desired. Furthermore, the heat dissipation device 102 may beconstructed from a thermally conductive material such as copper,aluminum, alloys thereof, and the like. Numerous methods for formationmay be incorporated to fabricate a device such as heat dissipationdevice 102, including die casting, machining, or molding, but theclaimed subject matter is not limited to any particular method offormation.

FIG. 2 shows an oblique view of a heat dissipation device 102, shown ina non-mounted configuration. As shown in FIGS. 1 and 2, the heatdissipation device comprises a base portion 118 with a mounting surface114 and an opposing dissipation surface 116. A plurality of projections112 may be formed on the heat dissipation device 102, and may extendsubstantially perpendicular from the base portion dissipation surface116. The projections may include elongate planar fin-like structures orcolumnar/pillar structures, and may be formed during the formation ofthe heat dissipation device, for example. Heat dissipation device 102may preferably be formed in a molding process, but numerous othermethods or combinations of methods of formation may be used inaccordance with at least one embodiment.

As shown in FIGS. 1 and 2, a plurality of channels 110 may extend fromthe dissipation surface 116 to an opposing mounting surface 114 of thebase portion 118 of the device 102. At least one channel 110 may besubstantially perpendicular to the base portion dissipation surface 116,although numerous configurations may be used in alternative embodiments.In this particular embodiment, a plurality of channels 110 are formedaround the periphery of the base portion 118 of the device 102. Themethod of formation of these channels may vary, and any method orcombination of methods of formation that results in at least one channelbeing formed in the base portion of a heat dissipation device is inaccordance with the claimed subject matter. One method of formation maycomprise a series of saw processes, where a sawing tool is applied toselected areas of the base portion 118 of the device 102, resulting inthe formation of a plurality of channels 110. Additionally, one or moredrill processes may be used to form one or more channels 110, or thechannels may be formed in the initial molding process of the device 102,for example. It may be desirable, in the formation of one or morechannels 110, to provide a portion of the mounting surface 114 free ofone or more channels at least as large as the top surface of amicroelectronic device 104, in order to ensure proper mounting to device104, as shown in FIG. 1.

Referring now to FIG. 1, airflow from a fan 128 may travel parallel tothe projections 112, into the one or more channels 110. At least aportion of the air may travel through and exit the one or more channels110, and may travel across the top surface 109 of the substrate carrier108. This may result in heat dissipation in one or more secondarycomponents 130, which may include, for example, one or more voltageregulators, but the claimed subject matter is not so limited. Heatdissipation of these one or more secondary components may be byconvective cooling, which may result from the airflow passing throughthe one or more channels 110.

It is important to note that the air channel configuration may vary indiffering embodiments of the claimed subject matter. For example, theone or more air channels 110 are illustrated in FIGS. 1 and 2 as havinga rectangular cross sectional shape. However, the air channels may haveany appropriate shape, including but not limited to elliptical,triangular, or the like. Additionally, the air channels may take on anydirection or configuration. The air channels in FIGS. 1 and 2 are shownas being perpendicular to surfaces 114 and 116 of device 102, but inalternative configurations, one or more air channels 110 may be formedto run diagonally from the surfaces 114 and 116, and may have multipleoutlets, for example.

In an alternative embodiment of the claimed subject matter, there isillustrated in FIG. 3 an alternate view of a microelectronic assembly101 comprising a heat dissipation device 102 attached to amicroelectronic die 104. The microelectronic die is physically andelectrically attached to a substrate carrier 108 by a plurality ofsolder balls 106. A plurality of channels 110 may be formed on thedevice 102. One or more secondary components 130, which may include, forexample, one or more voltage regulators, may be formed on substratecarrier 108. A shroud 126 may be formed proximate to the heatdissipation device 102, and may be attached to the top surface 109 ofsubstrate carrier 108. Shroud 126 may be formed out of plastic by use ofone or more injection molding processes, but the claimed subject matteris not limited to any particular material or formation process. Shroud126 may enhance or alter airflow across the top surface 109 of thesubstrate carrier 108, by directing the airflow in a particulardirection, for example. In operation, shroud 126 may direct air passingthrough channels 110, and cause air to flow over one or more secondarycomponents 130 rather than dissipate, for example. It is important tonote, however, that the claimed subject matter is not limited to use ofa shroud, or is a shroud limited to a configuration illustrated in FIG.2, but any configuration that results in enhanced airflow across asubstrate may be in accordance with the claimed subject matter. Theembodiment illustrated in FIG. 3 may be advantageous for use in amicroelectronic assembly that incorporates one or more secondarycomponents mounted on the secondary side of a substrate, where heatdissipation of these components may be desirable, for example.

In another alternative embodiment of the claimed subject matter, thereis illustrated in FIG. 4 a microelectronic assembly 103 comprising aheat dissipation device 102 attached to a microelectronic die 104. Themicroelectronic die is physically and electrically attached to asubstrate carrier 108 by a plurality of solder balls 106. A mountingsurface 114 of a base portion 118 of the heat dissipation device 102 isattached to one surface of the microelectronic die 104, preferably by athermally conductive adhesive (not shown). A plurality of channels 110may extend from the dissipation surface 116 to an opposing mountingsurface 114 of the base portion 118 of the device 102. The plurality ofchannels 110 may be substantially perpendicular to the base portiondissipation surface 116 in one embodiment. In this particularembodiment, a fan 122 may be mounted to a plurality of support members120. The support members 120 are shown as being mounted to device 102 bypassing through substrate carrier 108, but alternative embodimentsexist. For example, fan 122 may be mounted by use of one or more supportmembers 120 to the secondary side 107 of the substrate carrier 108. Inoperation, tan 122 may provide airflow to the secondary surface 107 ofthe substrate carrier 108. A substantial portion of the air may becaused to flow parallel to the secondary surface 107, which may resultin airflow being provided to one or more secondary components 124. Thisairflow may result in some amount of heat dissipation for the secondarycomponents 124. The embodiment illustrated in FIG. 4 may be advantageousfor use in a microelectronic assembly that incorporates one or moresecondary components mounted on the secondary side of a substrate, whereheat dissipation of these components may be desirable, for example.

FIG. 5 illustrates a substrate secondary side modification that may beincorporated for use in one or more of the illustrated embodiments, suchas the secondary side fan configuration of FIG. 4. Shown in FIG. 5 is asecondary side view of a substrate carrier 108. The substrate carriersecondary side 107 may have formed thereon a plurality of solder balls136. The plurality of solder balls 136 may be formed on opposing sidesof a microelectronic device footprint 138, for example. In operation,the secondary side solder balls may be utilized in the microelectronicassembly of FIG. 4, and may provide enhanced heat dissipation for one ormore secondary side components 124. Enhanced heat dissipation may beprovided in the following manner: airflow may be provided from a fansuch as fan 122 of FIG. 4. At least a portion of the airflow may flowparallel to secondary surface 107, and may, when encountering theplurality of solder balls 136, undergo an increase in turbulence. Thisincrease in turbulence may result in enhanced heat dissipation of one ormore secondary side components 124 as compared to the heat dissipationprovided by laminar airflow. Formation of the solder balls 136 may beperformed in a variety of ways, including one or more wave solderprocesses. It is important to note, however, that the claimed subjectmatter is not limited to use of any particular formation method, but anymethod of fabrication that results in the formation of a plurality ofsolder balls on the secondary side of a substrate carrier is inaccordance with the claimed subject matter.

It can be appreciated that the embodiments may be applied to theformation of any semiconductor device wherein heat dissipation may bedesirable. Certain features of the embodiments of the claimed subjectmatter have been illustrated as described herein, however, manymodifications, substitutions, changes and equivalents will now occur tothose skilled in the art. Additionally, while several functional blocksand relations between them have been described in detail, it iscontemplated by those of skill in the art that several of the operationsmay be performed without the use of the others, or additional functionsor relationships between functions may be established and still be inaccordance with the claimed subject matter. It is, therefore, to beunderstood that the appended claims are intended to cover all suchmodifications and changes as fall within the true spirit of theembodiments of the claimed subject matter.

1. A microelectronic assembly, comprising: a microelectronic die havinga back surface and an active surface; a heat dissipation device coupledto the microelectronic die back surface, wherein said heat dissipationdevice comprises: a base portion having a dissipation surface and asubstantially opposed mounting surface; at least one channel defined inthe base portion, wherein said at least one channel extends from saiddissipation surface to said mounting surface; a plurality of projectionsextending from said base portion dissipation surface; and a first fanmounted on at least a portion of said plurality of projections toprovide airflow substantially towards said at least one channel; asubstrate having a primary and a secondary side, wherein said substrateprimary side is coupled to said microelectronic die active surface; anda second fan coupled to the secondary side of said substrate, saidsecond fan positioned to provide airflow to at least a portion of saidsecondary side.
 2. The microelectronic assembly of claim 1, additionallycomprising a shroud formed between said fan and said base portion, saidshroud formed proximate to said plurality of projections.
 3. Themicroelectronic assembly of claim 2, wherein said shroud is positionedto enable airflow from said fan that passes through said at least onechannel to be diverted away from said heat dissipation device.
 4. Themicroelectronic assembly of claim 1, wherein said at least one channelis formed proximate to said one or more sides of said base portion. 5.The microelectronic assembly of claim 1, further comprising a pluralityof solder balls formed on the secondary side of the substrate, whereinsaid plurality of solder balls are formed proximate to said second fan.